Silver copper alloy



Patented Apr. 9, 1940 UNITED STATES PATENT OFFICE W. Wiggs, P. R. Mallory &

Indianapolis, Ind.,

00., Inc., Indianapolis,

assignors to Ind.,

a corporation of Delaware No Drawing. Original 1939, Serial No.

1 Claim.

This invention relates to a new silver-copper alloy for use as replacement of pure silver and for all uses to which previously known silver alloys have been employed, of which may be mentioned particularly, uses of the alloys of the present invention in connection with silver solders, electrical contacts, silverware, jewelry and dental applications.

This application is a division of prior filed copending application Serial No. 257,667, filed February 21, 1939.

It is one object of the present invention to provide an alloy which has improved electrical properties such as electrical conductivity.

It is a further object of the present invention to provide an alloy which shows great fluidity in the molten state and lends itself to casting of very intricate shapes.

It is a further object of the present invention to produce an alloy which has improved wetting characteristics when used as a silver solder.

A still further object is to produce a new alloy which has superior electrical characteristics when used as an electrical make-and-break contact such as low material transfer, low contact resistance and freedom from welding or sticking. Other objects of the invention will be apparent from the following description taken in connection with the appended claim.

The present invention comprises the combination of elements, methods of manufacture and the product thereof brought out and exemplified in the disclosure hereinafter set forth, the scope of the invention being indicated in the appended claim.

While a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in themethod of procedure and the combination of elements without departing from the spirit of the invention.

The present invention contemplates the addition of lithium and copper to silver base alloys. In the formation of the alloy it is preferable to provide a composition of the materials specified in the following proportions by weight:

Percent .002 to 3 35 to 50 Lithium Copper in excess of 5 Balance substantially all silver. a

257,667. Divided application January 5, 1940, Serial No.

application February 21, and this 312513 We have also found may also be added to of the new alloys of that the following elements improve the characteristics the present invention:

Percent 5 Cadmium Up to 25 Zinc Up to 28 Tin Up to 11 Manganese Up to 20 Nickel Up to 1o Phosphorus Up to 8 Silicon Up to 2 Magnesium Up to 8 Beryllium Up to 3 Calcium Up to 2 In addition to these baser elements, materials from the palladium, platinum or gold group may also be present up to 10% each.

The alloys of the present invention may be prepared by melting the ingredients together in the correct proportions. The lithium is preferably added in the form of a silver-lithium master alloy, containing approximately of lithium. This master alloy has a very low melting point which is in the neighborhood of 410 to 450 C. and therefore will go readily into solution when added to the silver-copper melt.

The effect of lithium is to completely 'deoxidize the silver melt and to free it from other impurities which are harmful. Part of the lithium will be eliminated together with these impurities and the remaining melt will be free from inclusions and oxides. The presence of lithium also prevents the further oxidation of the melt during the heating periods to which the melt may be subjected and the material retains a very high fluidity during pouring, resulting in extremely clean castings.

We have found that coin silver containing a small percentage of lithium such as, for instance, .01% or less will lend itself much more readily to rolling and wire drawing operations, resulting in a material which is entirely free from surface blemishes and oxide stringers. Furthermore if such silver wire is being spun or if silver wire produced in that manner is being headed a suriace'finish can be obtained with alloys of the new invention that excels anything obtainable so far with alloys of the prior art. Very often in heading of coin silver wire the formation ofv edge cracks or splits is encountered, causing a great number of rejects. By using the addition of lithium in these alloys in the proportions specified these dimculties can be eliminated or at least materially reduced.

If lithium is used in higher proportions such as .05 to 1% we have found that alloys of the coin silver type will show greatly improved electrical characteristics. Contact alloys of this type have very improved characteristics as far as material transfer and contact resistance are concerned. It was also of great interest to find that the material transfer for this composition was from the cathode to the anode. In most silver base alloys the material transfer is in the opposite direction, therefore it seems desirable to use the material of the present invention in combination with another silver alloy having opposite transfer characteristics.

Since lithium decreases the melting point of silver very materially and since an eutectic is formed at 2.7% lithium, having a melting point of 610 C. care must be exercised if these materials are being processed at elevated temperatures and if they contain higher percentages of lithium. By proportioning the ingredients correctly the and advantages, has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claim.

What is claimed is:

An alloy containing .002 to 3% lithium, from greater than to copper and the balance substantially all silver.

FRANZ R. HENSEL. KENNETH L. EMIVIERT. JAIUES W. WIGGS. 

